1. Field of the Invention
This invention relates to a method and apparatus for in-place sterilization of fermentation equipment including liquid media.
2. Description of the Related Art
It is known that an autoclave can be used to sterilize articles used in fermentation, such as a fermentor vessel. U.S. Pat. No. 4,111,654 describes an autoclave apparatus including a chamber in which articles are steam sterilized. The chamber is surrounded by an outer space having a steam supply conduit. A constant pressure difference between the chamber and the outer space permits thermodynamically optimum steam flow to the chamber with minimal energy loss. However, the use of an autoclave for sterilization has the shortcoming that the articles must be removed from the fermentor, transported to the autoclave and placed inside the autoclave.
U.S. Pat. No. 5,026,524 describes an apparatus to subject culture media and instruments to temperatures below 100.degree. C., as defined as low temperature sterilization. A sterilization chamber is provided for placement of articles therein. A jacket chamber surrounds the sterilization chamber and is operated to subatmospheric pressure. Steam is introduced into the jacket chamber for providing a preselected temperature within the sterilization chamber. This patent does not disclose in-place sterilization of fermentation equipment.
U.S. Pat. No. 4,324,762 describes an apparatus for sterilization of liquid media used for growing microorganisms in a fermentor. A sterilization vessel includes a heater, heat exchanger, inlet and outlet pipes. A buffer vessel communicates with the sterilization vessel. Initial liquid media is contained in the sterilization vessel and is heated to a sterilization temperature with the heat exchanger. The sterile medium flows from the sterilization vessel to the buffer vessel and is intermittently or continuously supplied to the fermentor. This patent provides in-place sterilization of the medium but does not provide in-place sterilization of the fermentation equipment.
Conventional bench fermentors have provided in-place sterilization of fermentor vessels with external steam or internally produced steam. Typically, the fermentor vessel is formed of high temperature resistant glass or stainless steel with glass windows. Fermentor vessels formed of stainless steel with glass windows have the disadvantage of limited visibility of the fermentation process taking place within the vessel. During the sterilization, a research fermentor with a glass cylinder is still one of the preferred designs. During the sterilization, steam is introduced inside the glass fermentor vessel from an input port. As a result of the introduction of steam or heat, pressure inside the fermentor vessel is greater than atmospheric pressure outside the vessel. This fermentor has the disadvantage that if the glass of the fermentor vessel is weak due to a scratch, blemish or the like, the increased pressure within the vessel can cause the glass of the vessel to break crack or become displaced.
It is desirable to provide an improved assembly for in-place sterilization of fermentation equipment and liquid media.